Dust cloth



Oct. 11, 1960 Q w, ENGDAHL 2,955,962

DUST CLOTH Filed Sept. 28. 1956 DUST cLorH Gordon W. ngdahl, St. Paul,Minn., assignor to Minnesota Mining and Manufacturing Company, St. Paul,Minn., a corporation of Delaware Filed sept. 2s, 1956, ser. No. 612,871

713mm. (ci. 117-140) This invention relates to a new article ofmanufacture, and in particular, relates to a new type of dust clothcomprising a thin, readily conformable and pliable web lightly sizedwith la minute quantity of a rubber-resin type pressure-sensitiveadhesive substance.

In household cleaning, it is desirable to remove dust and foreignparticles frornva surface without raising or spreading the dust orforeign particles through the air, or smudging, soiling or otherwisecontaminating the surface. Many presently marketed cleaning materialsfor this purpose have an oily or waxy base. Thus they cause lightsurface films of wax or oil to be deposited during cieaning. Suchdeposits are not always desirable, and in many cases, soil or interferewith the beauty of certain natural finishes on furniture. Moreover, oilydeposits on a surface tend to attract dust, and the dust free appearanceof such a surface is short-lived.

Additionally, dust cloths impregnated with an oily or waxy base aremessy to use in that transfer of the oil or wax from the dust cloth tothe hand occurs.

The use of industrial tack rags for household cleaning does not providea ready expedient. One such type of tack rag is formed by dipping acloth in varnish, and allowing the. varnish to partially dry until itreaches a suitably tacky state. But this type of ltack rag is messy touse, and has only a short useful life, gradually losing its tack andbecoming too stili to conform to a surface during cleaning.

Another type of industrial tack rag employs certain chlorinatedcompounds -to gain tackiness. Most of these compounds, however, areknownto be toxic under certain conditions; thus they are generallyunsuitable for household use, where the possibility exists that a smallchild will play with a dust cloth, and even place it in his mouth.

The art, therefore, is sorely in need of an improved type of householddust cloth which does not leave an. oily deposit, or the like, whenused, which can be stored' for lengthy periods under ordinary storageVconditions Without loss of its required properties, and which is nottoxic. This invention provides such an article.

The article hereof possesses the particular advantage of being andremaining highly exible and pliable for an almost unlimited period oftime. It may be characterized as non-stiffening. It can be formed so asto be nontoxic. In use, it can be pressed readily into conformity withgradual surface irregularities to pick up foreign particles such as dusttherefrom Without leaving a waxy or oily deposit on the surface. Dustand foreign particles readily cling to my dust cloths; yet my dustcloths do not stick or cling to surfaces over which they are lightlyrubbed or passed to accomplish cleaning.

or the like into the air.V

One of the materials used in fabricating my articles is well known inthe pressure-sensitive adhesive tape art as a rubber-resin typepressure-sensitive adhesive sub-VV stance; Pressure-sensitive adhesivesin the tape' art haveY nited r States atent Using my i dust cloths,surfaces can be cleaned without raising dust the property of beingaggressively and stably tacky; and when such tapes are applied tosurfaces under light finger pressure, they cling with such tenacitythat, usually, greater force must be employed to separate them from thesurface than was originally employed during their application. Slidingsuch adhesives over surfaces with ease and without tenacious clinging tothe surface has heretofore been a property, the lack of which has beennotorious in pressure-sensitive adhesive articles; yet, such a propertyis, surprisingly, patently evident in the new articles hereof, eventhough pressure-sensitive adhesive substances constitute an essentialand even primarily functional part of my articles.

I have found that by employing extremely small amounts ofpressure-sensitive adhesive substances, amounts heretofore consideredinsuicient to provide a product having any usefulness or utility, and byemploying such small amounts in combination with a thin, pliable, highlyporous web of fibers, it is possible to achieve the surprising result ofproviding a highly useful dust cloth article possessing an unusual andunexpected combination of desirable properties, as aforesetforth.

A drawing, containing descriptive legends, is made a part hereof andwill serve .to further illustrate the article of this invention.

The amount of pressure-sensitive adhesive substance which I employ inmaking my articles is far below the amount customarily employed in thefabrication of pressure-sensitive adhesive articles. I do not useamounts in excess of 3 grains per 24 square inches of lthin webmaterial. Preferably I employ only approximately 1 to 2 grains per 24square inches of web material, or even smaller amounts, whereas theamount of pressure-sensitive substance employed -in thepressure-sensitive tape art is always in excess of about 5 grains per 24square inches of tapebacking, and customarily has been even as high as20 or more grains per 24 square inches of backing. As aforestated,greatly lower amounts have heretofore been considered unsatisfactory toprovide useful articles.

For the web material of my new articles, I employ thin, readilyconformable and pliable, highly porous, brous web or sheet materials.The web may be formed from laments or fibers of such materials as, forexample, cotton, rayon, linen, wool, synthetic substances, etc. The webmay be woven or unwoven; it may be comprised of a regular network ofintermeshed fibers such as, for example, cheese cloth, or it may becomprised of irregular randomly oriented fibers. It may be somewhatfelted,

or even napped, but in all cases it is highly porous, having an openstructure of entangled or intermeshed fibers, `and is thin. If the webis held near the eyes, objects on the other side of the web can be madeout through the openings or pores of the web; the web is not a solidsheet such as employed as backings in the pressuresensitive tape art.

Likewise, my dust cloth sheet article is highly porous; it is not aunied, d e., impregnated, sheet such as employed as the backing forcertain pressure-sensitive adhesive tapes.

A preferred, but non-limitative example of my dust cloth and a methodfor making the same will now be illustrated.

Example I The porous web of thisY example was Vformed from Viscose rayonbers in the following manner. A tow Y consisting of a mass ofsubstantially aligned, untwisted,

1.5 denier, viscose rayon filaments was cut into 2 lengths to gain amass of substantially untwisted staple fibers. 'Ihese short fibers werethen formed into a mat using a felting machine such as sold bytheCurlator Corporation under then trade-name ,Rando-Webber. The fiberswere fed into the felting machine on a 4travelcatalyst;

3 ing belt'which carried the fibers under a very nely toothed or knurledroll. 'I'he roller teeth in this machine are so ne that they pick uponly one nber--or at most only a few fibers-at a time from the belt, andshift thebers into a rapidly moving airstream which carriesV themsuspended in air through a'venturi: After passing through the venturi,the suspended bers` are deposited in random orientation upon a rotatingrelativelyY large condensing roll which contains ineperfora-- tionsVthrough which the air. iswithdrawnl from thesuspensionwhile .the fibersare filtered out'to lform-.a matted web. The fibers of the webare'twisted and intermingled during its-formation, and this "imparts a'certain amountY of strength .to the web, i.e.,lsuiiicientfstrength topermit -the vweb to be handled carefullyl 'without its falling apart.'Vl

A highly porous matted web having a d ry weight of 1/2V ounce pers'quareyard and a maximum thickness of about 4' mils Was formed using the aboveprocedure. After forming theweb, one may wind it into a storage rollusing an interliner to separate the convolutions in the roll.Preferably, vhowev er,-the web isV taken directly off the condensingroll and vsatl'lrated'with a dilute solution of a rubber-resin-typelpressure-sensitive adhesive substance.

The rubber-resin type pressuresensitive adhesive substance usedto vformthe dust cloth of thisV example was a single polymer inherentlypossessing the proper balance of properties required for such adhesivesubstances, as particularly set forth below; To form the polymer,

v300 parts by weight of methyl visoamylacrylate monomer 'werepolymen'zed ina solution of 700 parts ofV ethyl acetate solvent using 2parts o fbenzoyl peroxide as a The solution was'held at 60 C. undercontinuous agitation for 5 hours until the polymerization was largelycompleted, and then'rais'ed to 70 C. for about one hour. A Viscoussolution containing about 30% non-volatiles resulted. Thisv solution wascooled to room temperature and dilutedto about 1 O% nonvolatiles withadditions of heptane to provide a very dilute Vand highly fluidmixture.VA

The non-woven web 'formedgabove Ywas carefully drawn through this dilutesolution'of adhesive'f After thus saturating the web, it wasdried Vbypassing it at a *speedof about v yards Vperminute over successive hotcans held'atV about y9( C. There resulted a V coating Vweight orconcentration of polymethyl Visoan'lylacryla-te of about l to 2 grainsper 24 square inches of web. The finished webY was still highly porous;the amount of polymethyl Visoarnylacrylate onl the web `was insufficientto unify' the Web or lill its pores', but was suicientwto lightly size,i.e., Yessentially coat, vi'rnjlividujal 'fibers or fibrous elementsVofthe web. Further, the individual nbers'of points of intersection'bythe very small amount of pressure-sensitive adhesive substance appliedthereto, and

Ythe finished dust cloth couldbe subjected to ordinary .mat ofintermixed and randomly oriented fibers.

' ple, or withirelated Aadhesive substances consisting largely of aVsynthetic saturated polymeric material which in herently possesses therequired four-fold balance of properties for a rubber-resin typepressure-sensitive adhesive, as hereinafter defined, constitute thepreferred dust cloths of this'invention for the reason that they areparticularly resistant to aging, and exhibit very little tendency toVbecome stiff even after extremely prolonged storage.

" 1 The yfollowing .non-limitative examples further Villustrate the new`dust Vcloths of this invention.

YExemple 2 t The Web used in making the dustlclotli of this exam- .plewas'formed according to the following procedure: A.mixture of. about.40% thermoplastic cellulose acetate be'rs'and .60% non-thermoplasticviscose (regenerated celluloseor rayon) fibers were carded to form aporous The thermoplastic cellulo'selacetate fibers Were of about 3`denier siz'e andr 1.25 inches long. ,The viscose fibers were about 1.5denier and 2 inches long. The porous mator web ofthese fibers was passedthrough a system of .heated rollsso as to lightly press and heat thefibers of the web, and cause the thermoplastic fibers to interbond attheir points of. intersection. As a result'of this treatment, theviscose fibers remained randomly oriented through the randomly oriented.and interbonded network Vthe web were somewhatl bonded Vto each otherat their ofthermoplastic bers, and were looselyheld-in the network Vbymechanical restraint and Yfrictional contact. After thisV step, the webwas Vlightly moistened with -water and passed between a pair ofresilient squeeze rolls, over a series Vof supporting rolls, and througha second pair lof resilient squeeze rolls. The latter pair -of squeeze.rolls wererotated .at a rate'ofspeed somewhat greater than the rstpair. The supporting rollswere `located Vin a tunnel through which theweb passed and in which a heated atmosphere .of steam was maintained.The

vheat and steam served to maintain ythe fibersV of the web in YaVsoft'condition and prevented themY from drying out during thestretching operation conducted'between the pairs of squeeze rolls.yAfter the web was stretched, it was `cooled to room temperature andthereby fixed in its stretched condition.

A web of this type is suitably stretched to an extent suticient toreduce its width by at least about 20%. This jcauses theiibers of theVweb to be slightly turned and handling, such as encountered in dustingoperations,

without individual fibers of the -web falling or Vlinting 'i out.

The finished dust cloth was Wound upon itself into a roll, and for theconvenience of`users, is desirably marketed in this form. The ysurfacesof the clot were.

found not to sticktogether inthe roll, and it could` be easily unwoundand cut into suitable lengths for dusting use. Instead of winding-alength of the dust cloth mat terial into a roll, it can immediately becut into Aclust (cloths of suitable s ize, and the lothsgflded and con jventionallypackaged for/marketing'. i

The dust cloth of this,exampleVV was Softand easily folded, crumpled,etc. It could becrurnpIednto a ball and thereafter unfolded and fiatter1 ed 5i1tf withease Surfaces ofthe dust clothididnot'stick togetherj yetv t when used to clean a surface, vdustfand foreign particles .readilyclung 1 the ClO-fh- The P0rl11enatur-fthe f weak.

width by simply pulling in a crosswise direction to its crowdedytogether in a lengthwise direction, and imparts a considerablelengthwise strength to the web, so that when it is jerked lengthwise itproduces a clothlike snapping sound. Width Vstrength of the web is, ofcourse, It may relatively easily be stretched across its length. J

A highly porousp1iable.web formed ink the Vforegoing manner, `andlhaving a weight Yof about 0.6 ounce per square yard and a maximumthickness of about 4 mils,

was saturated with adilute solution of a pressure-sensitive adhesivesubstance containing the following ingredients:

. Parts by weight Polyvinyl ethyl ether ...L 100 Terpenephenolic resin15 V Antioxidant 2 The vinylhether vused hadn inherent viscosityof about3.2 as calculated from the viscosities of dilute solutions in benzenesolvent as measured on the Ostwald viscometer. The terpene phenolicresin is a commercial resin sold by Newport Industries, Inc. under thetrade-name Newport S and is believed to consist of the condensationproduct of a Friedel-Crafts type reaction between phenol and alphaandbeta-pinene, and -to comprise about 2025% phenol by' weight. Theantioxidant was 2,5 ditertiary amyl hydroquinone.

The ingredients above were dissolved in a mixture of about 20 partsethanol and 1200 parts toluene to form a dilute solution. This dilutesolution was sprayed upon the web in an amount sufficient to provide,upon evaporation of solvent, a coating or concentration of approximatelyl to 2 grains of adhesive substance per 24 square inches of webmaterial. The sprayed web was then dried of solvent by passing it oversuccessive hot cans at about 80 C. to form a highly porous dust clothhaving properties comparable to those of the cloth of Example l. Again,the fibers of the web were lightly sized with the pressure-sensitiveadhesive substance.

Example 3 Another dust cloth was formed by saturating the web of Example2 with a dilute solvent solution of the following pressure-sensitiveadhesive ingredients:

Parts by weight Pale crepe natural rubber 100 Piccolyte S-l15 resin 85Antioxidant of Example 2 1 The Piccolyte S-1l5 resin, sold byPennsylvania Industrial Chemicals Corporation, is a polyterpene resinmelting at about 115 C., with essentially zero acid number.

The rubber and antioxidant were first milled together on a rubber milluntil the rubber mass was rendered smooth and uniform. The resin andmilled mass were then dissolved in la mixture of 25 parts of ethanol andExample 4 Another dust cloth was formed using a web consisting of anopen-weave cotton cloth known as cheese cloth. The followingpressure-sensitive adhesive blend was used.

Y Parts by weight High molecular Weight polyisobutylene 100 Antioxidantof Example 2 1.1 Low molecular weight polyisobutylene 70 Hercolyn resin3G Piccolyte S-85 resin 45 The high molecular weight polyisobutylene(commercially available as Vistanex B-120) was a non-tacky rubbery orelastomeric polymer of isobutylene monomers, whereas the low molecularweight polyisobutylene (commercially available as Vistac No. 1, lndopolH300) was a highly tacky resinous type polymer. Hercolyn resin ismarketed by the Hercules Powder Company and is stated by themanufacturer to be largely methyl dihydroabietate. Piccolyte S-85 resinis a polyterpene resin melting at about 85 C., with essentially zeroacid number.

The high molecular weight polyisobutylene and antioxidant were milled ona rubber mill to render the rubbery polyisobutylene smooth and uniform.Thereafter, all components of the adhesive substance were dissolved insuicient heptane to form a solution containing only about solids byWeight. The cheese cloth web was sprayed with the resulting diluteadhesive Solution, and the solvent evaporated. A weight of about 1 to 2grains of adhesive per 24 square inches of web was used, and wasjust'suicient to lightly size the individual fibers of the woven cheesecloth.

The treated sheet was effective in removing dust from polished surfaceswithout leaving any stain.V It did not feel sticky to the lingers, andwas easily folded or rolled into a ball and again unfolded duringdusting operations. When soiled, it could b e rinsed out in water anddried for further use.

Various pressure-sensitive adhesive substances may be used to form thedust cloths hereof. Examples of typical rubber-resin typepressure-sensitive adhesive may be found in U.S. Patents Nos. 2,236,527,2,410,078, 2,410,- 089, 2,438,195, and 2,553,816. These adhesives aregenerally formed from at least two components, i.e., a rubbery materialand a resinous tackier material, from whence they get the namerubber-resin pressure-sensitive adhesives. They have a rubbery basematerial, either natural or synthetic, which provides cohesion (internalstrength) and elasticity (a retractive force when stretched andretraction when released after stretching). The rubbery material ismodied by blending with a compatible tackier resin (such as a rosin orester gum) which serves to increase adhesion (tackiness) and decreasecohesion with an attendant increase of stretchiness (elongation underlow stresses) and decrease of elasticity. These rubber-resin typeadhesives have a proper four-fold balance of adhesion, cohesion,stretchiness and elasticity; and when they are used in the manufactureof pressure-sensitive adhesive tapes, this balance of properties impartsto the resulting tape the characteristic of being aggressively andstably tacky, and yet capable of being stripped back from a smoothsurface to which it is temporarily applied Without delamination,splitting, or oisetting of adhesive.

lAs indicated above with respect to Example 1, certain Vsyntheticpolymers are inherently pressure-sensitive and possess the requiredfour-fold balance of properties. They are equivalents of rubber-resinadhesives and are regarded as of the rubber-resin type. A furtherillustra- 'tive example of such a synthetic polymer, and one useful informing the articles hereof, is a 75:25 copolymer of2-ethyl-butyl-acrylate and ethyl-acrylate.

This invention Will be seen to provide an entirely new and usefularticle of commerce which, while formed from well known materials,possesses properties heretofore not associated with such materials. Nopresently available dust cloth known to me possesses all theadvantageous properties possessed by my article, such propertiesincluding that of being and remaining pliable and flexible even afterlong periods of storage, that of being non-toxic, that of readilypicking up dust and holding onto the dust particles, and yet not leavingresidual surface lms or deposits such as oil upon surfaces over whichthe cloth is passed in cleaning.

That which is claimed is:

`1. A storable, non-toxic, porous, readily conformable and pliable dustcloth to which dust readily clings, said dust cloth being easilyslidable over surfaces under light linger pressure without clinging tothe surfaces and without depositing foreign materials thereupon, andbeing easily unfolded and attened without surfaces of the cloth stickingtogether after being crumpled into a ball, said dust cloth comprising athin non-unied, porous web of fibers, said web having an open structureand having a weight on the `order of about one-half ounce per squareyard, and a small quantity of an adherent rubber-resin typepressure-sensitive adhesive substance lightly sized upon the iibers ofsaid web, the quantity of said adhesive substance being not in excess of3 grains per 24 square inches of said web.

2. A storable, non-toxic, porous, readily conformable and pliable dustcloth to which dust readily clings, said dust cloth being easilyslidable over surfaces under light 7 finger pressure Without clinging tothe surfaces and Without depositing foreign materials thereupon, andbeing ,easily unfolded and attened without surfaces VVof .the ,clothsticking together after being crumpled into a. ball, said dust clothcomprising a thin, non-unified, highly porous web of fibers, said webhaving an open structure and having a Weight on the order ofabout-one-half ounce per Vsquare yard, and asmall quantity ofY an.adherent rubberresin type pressure-sensitive Vadhesivesubstance lightlysized upon the .fibers of said Web, therfquantity of saidadhesivesubstance being approximately 1 to 2 grains per 2 4 `square inches ofsaid web. f Y Y f 3. A Vstorable, Vndnatcxic, porous, readilyconformable dust cloth being easily slidable over surfaces under lightfinger pressure Without clinging to the surfaces and `Without depositingforeign material thereupon, and being easily unfolded and flattenedWithout surfaces ofthe cloth sticking together after 'being crumpledinto a ball, said dust cloth comprising a thin, non-unified, highlyporousrweb of fibers, said Web having an openvst ructure and having aWeight on the order of about one-half ounce per square yard,Y and asmall quantityiof an adherent rubber-resin type pressure-sensitiveadhesive substance consisting es-V sentiallyof a saturated polymericmaterial lightly sized upon the fibers of said web, the quantity of saidadhesive substance being not `in excess of 3 grains per 24 square inchesof said web. Y Y Y 4. YThe articleV of claim 3 wherein the saturatedpolymeric material is polymethyl isoamylacrylate.-v

5. As a new article of manufacture: a roll of a length and pliable dustclothy to which dust readily clings, said lzi115 not in excess of 3grains per 24 square inches of said web. 6. As a new article ofmanufacture: a roll of a length `lof storable,vnon,toxic, porous,readilyconformable and surefsensitive adhesive l'substance consistingessentially Yofa saturated polymeric material lightlysized upon thefibers `of saidweb, the Aquantity of `said adhesive substance being notin excess of 3 Ygrains. per 21,4 square inches of said web. Y Y

7. A storable, non-toxic, porous, readily conformable `and pliabledustcloth to Ywhich Y,clust readily clings, said dust cloth being easilysllidable over Ysurfaces underV light finger pressure Without clingingtothe surfaces and Without depositing foreign material thereon, and beingeasily unfolded and attened without surfaces of the cloth stick- 'of astorable, non-toxic, porous, readily conformable and pliable dust clothsheet material to which dust readily clings, said dust cloth sheetmaterial Vbeing .easily un- Wound -from said roll withoutY surfacesthereof sticking together, being easily slidable' over surfaces underlight finger pressure without clinging to the surfaces and Withoutdepositing foreign materials thereupon, and compris ing `a thin,non-unified, highly porous Web of fibers, said web having an openstructure and having a Weight on the order of about one-half ounce persquare yard, and

asmall quantity of an adherent rubber-resin type pressure- Vsensitiveadhesive substance lightly sized upon the bers of said web, thequantityof said adhesive'substauce being ing together after lbeing crumpled intoa `ball, Vsaid dust cloth comprising athinnon-unied, porous web ofnonwoven, intermiugled fibers, said web having `an open' structure andhaving -a weight on the order of about onehalf ounce per square yard,and a small quantity of an adherent rubber-resin type pressure-sensitiveadhesive substance lightly sized upon the bers of said Web and serving,in addition to its function as a material to which dust clingsfto bondvarious'of said ibers'together at their Ypoints 4of' intersection,Y thequantity of said adhesive substance being not in excess of 3 grains perV24 square inches of said web. Y Y

References Cited in the le of this patent Y VUNiTED STATES, PATENTS1,633,076

Dorsey June 21, 1927 2,438,195 Tierney Mar. 23, 1948 2,528,602 MagirtNov. 7, 1950 2,719,806 Nottebohm Oct. 4, 1955

1. A STORABLE, NON-TOXIC,POROUS, READILY CONFORMABLE AND PLIABLE DUSTCLOTH TO WHICH DUST READILY CLINGS, SAID DUST CLOTH BEING EASILYSLIDABLE OVER SURFACES UNDER LIGHT FINGER PRESSURE WITHOUT CLINGING TOTHE SURFACES AND WITHOUT DEPOSITING FOREIGN MATERIALS THEREUPON, ANDBEING EASILY UNFOLDED AND FLATTENED WITHOUT SURFACES OF THE CLOTHSTICKING TOGETHER AFTER BEING CRUMPLED INTO A BALL, SAID DUST CLOTHCOMPRISING A THIN NON-UNIFIED, POROUS WEB OF